Abstract: In this paper the changes of solubility, Ca2+-ATPase activity and total sulfhydryl content of myofibrillar protein of Aristichthys nobilis surimi were investigated after they were frozen with 0%, 1%, 3%, 5% soluble soybean polysaccharides (SSPS) for 12 weeks at -18oC. Myofibrillar protein structure changes during frozen storage were also analyzed based on the Fluorescence spectra and Raman Spectra. Results showed that the protein solubility, Ca2+-ATPase activity as well as total sulfhydryl content of frozen Aristichthys nobilis surimi presented two phases of dropping trend. They decreased sharply during the previous four weeks, but to a lower extent during the subsequent eight weeks. The addition of SSPS could reduce these changes to some extent and the best effect was obtained by 5% SSPS. The Fluorescence spectra and Raman spectra of 12-week frozen surimi also indicated that SSPS could prevent the exposure of aromatic amino acid residues, such as tryptophan and tyrosine, to a polar microenvironment on the myofibrillar protein surface. SSPS could also reduce the decrease of ɑ-helix content and prevent the conformational changes of disulfide bonds from gauche-gauche-trans (g-g-t) to gauche-gauche-gauche (g-g-g). The best effect was obtained by 5% SSPS. The results showed that SSPS could effectively mitigate the myofibrillar protein denaturation of Aristichthys nobilis surimi and improve their quality during the 12-week frozen storage. Therefore SSPS is promising as a new protein cryoprotectant.

Key words: soluble soybean polysaccharides, Aristichthys nobilis surimi, myofibrillar protein, frozen denaturation, Ｒaman spectrum, fluorescence spectrum